1. Field of the Invention
The present invention relates to a thin-film magnetic recording head with a thin film which constructs a sensor or a heater beneath a main magnetic pole.
2. Description of the Related Art
For high density recording performed to the magnetic recording medium such as a hard disk and the like, a perpendicular recording type magnetic recording head that performs recording as perpendicularly applying a magnetic field to a magnetic recording medium has been used. Normally, such magnetic recording head is a thin film magnetic recording head having a multilayer structure in which plural thin films are laminated, and includes a thin film coil for generating a magnetic flux and a main magnetic pole for leading the magnetic flux to the recording medium. The main magnetic pole is formed by a manufacturing method in which a main magnetic pole material is embedded in a trench after the trench is formed by a photoresist. In the manufacturing method, a photoresist is applied onto a substrate on which components of the thin film head such as a reading element are accumulated, an exposure and a developing are performed to a region of the photoresist where the main magnetic pole is to be formed, and a trench for magnetic pole formation is formed. Then, an Al2O3 layer is formed on the photoresist and an electrode film for plating current supply is formed. After that, a high magnetic moment material (for example, FeCo), which is a material for the main magnetic pole, is plated, the photoresist is removed, and a planarization treatment is performed. As a result, the main magnetic pole is formed.
For the thin film magnetic recording head that performs perpendicular recording with a high density and an accurate writing width, it is very important to have the main magnetic pole with a highly accurate shape and size to the extent possible. In order to form a main magnetic pole with an accurate shape and size by the above-described manufacturing method, it is necessary to highly accurately perform an exposure and developing of a photoresist for forming a trench for magnetic pole formation.
The thin film magnetic recording head is normally used as being integrated in a slider that flies above a magnetic recording medium at a predetermined interval therebetween. In recent years, the distance between the slider and the magnetic recording medium is very small and approximately a few nanometers. When the slider approaches too much and contacts the magnetic recording medium due to an assembly error, a deformation of the magnetic recording medium, an impulse from the outside, and the like, either one or both of the slider and the magnetic recording medium may be damaged. Accordingly, a head disk interface (HDI) sensor that detects a flying height of the slider from the magnetic recording medium is provided in the slider. The HDI sensor is formed with a metal thin film such as NiFe, Ni, and the like. Also, a heater for flying height adjustment is provided in the slider, and the heater is formed with a metal thin film such as Ta, W, NiCr, NiCu, and the like.
In the case that the HDI sensor and/or the heater are/is provided in the slider, for a layout reason, the HDI sensor and/or the heater are/is positioned beneath the main magnetic pole, and the HDI sensor and/or the heater and the main magnetic pole may be overlapped from the perspective of a lamination direction. Hereinafter, a description is given using a case where the HDI sensor is positioned beneath the main magnetic pole as an example. In this case, as illustrated in FIG. 1, in the above-described manufacturing method, exposure light 20 irradiated to a photoresist 21 is transmitted through the photoresist 21 and an insulating layer 22 while exposing the photoresist 21 and reaches an HDI sensor 23. Then, the exposure light 20 is reflected at the HDI sensor 23. Then, reflection light 20a from the HDI sensor 23 is transmitted through the insulating layer 22, enters the photoresist 21 again from its lower side, and exposures the photoresist 21. The reflection light 20a from the HDI sensor 23 is not completely parallel and may be focused or diffused to some degree. When it happens, an exposure region of the photoresist 21 may expand and standing wave may occur, which does not allow the photoresist 21 to be exposed favorably. As a result, a trench for magnetic pole formation 21a (its outline is illustrated by two dot-dash lines) cannot be formed with favorable accuracy in size.
Also, the photoresist 21 is exposed by the exposure light 20 that has reached the photoresist 21 from an upper side (not-illustrated light source side) and the reflection light 20a that has reached the photoresist 21 from a lower side (HDI sensor 23). The reflection light 20a at the HDI sensor 23 disperses within an accumulation substrate in-plane, and the intensity of the reflection light 20a varies depending on a film thickness of an insulating layer (Al2O3 layer) 22 that is positioned at a lower side and the like. As a result, a variation may occur in the intensity of light which the region of the photoresist 21 where should be exposed receives within the accumulation substrate in-plane. When within the accumulation substrate in-plane a portion having a high light intensity and a portion having a low light intensity coexist, a variation occurs in a shape, especially a width, of the trench for magnetic pole formation 21a, so that a variation occurs in a width of the main magnetic pole embedded by an electrode film and plating. As a result, a variation occurs in a write width, which is important for a write characteristic. The write width is one of very important standards in a product specification.
As described above, when the trench for magnetic pole formation 21a having a favorable shape and size cannot be formed in the photoresist 21 due to the reflection light 20a from the HDI sensor 23, the shape and the size accuracy of the main magnetic pole deteriorate, the variation in the write characteristic increases, and a manufacture yield thereof decreases.